How do really long texts appear on old phones?

I know that when you send a really long text on an old phone it just splits it up and sends it as multiple messages, but I can't remember how a massive text appears when it's received on an old phone.

Is it strung back together into one text at the receiving end, or as randomly assorted mini messages? And is there a limit to how long a text an old phone can receive?

Thanks in advance.